Pivoting disc-type heart valve with two-piece base

ABSTRACT

A heart valve having a base cooperating with a free floating pivoting disc to control the flow of blood through the valve. The disc has a substrate covered with a coating of silicon-alloyed Pyrolite carbon. The base can be a one-piece housing having side arms or two members joined together to confine the disc in a pivoting relationship with the housing. The disc pivots about a chordal axis and rotates about its center. The two members of the base have substrates with coatings of silicon-alloyed Pyrolite carbon.

United States Patent Child ]*Sept. 17, 1974 PIVOTING DISC-TYPE HEART VALVE 3,416,159 12/1968 Smeloff et al 3 1 WITH TWO-PIECE BASE 1476443 "/1969 3,546,711 12/1970 [75] Inventor: Francis W. Child, Maple Plain, 3 594 324 7 971 Minn. 3.737,9l9 6/l973 [73] Assignee: The Regents 0f the University Of FOREIGN PATENTS OR APPLICATIONS Mmnesota Mmneapol's 1,160,008 7/1969 Great Britain 3/010. 3 Notice: The portion of the term of this g a i w June 1990 Primary ExaminerRichard A. Gaudet as een alme Assistant E.raminer--Ronald L. Frinks [22] Filed: Oct. 17, 1972 pp 298,237 57 ABSTRACT Related US Application Data A heart valve having a base cooperating with a free Division Of N0. March 1971. tfloating pivoting disc to control the flow of blood 3,737,919 through the valve. The disc has a substrate covered with a coating of silicon-alloyed Pyrolite carbon. The [52] U.S. Cl 3/1, 3/DIG. 3, l37/527.8 b am b a one-piece housing having side arms or [5 Cl. two members joined together to confine the disc in a Field of Searchw- [316- 3; 137/527, 527-4, pivoting relationship with the housing. The disc pivots 137/527-8 about a chordal axis and rotates about its center. The two members of the base have substrates with coatings References Cited of silicon-alloyed Pyrolite carbon.

UNITED STATES PATENTS 3,099,016 7/1963 Edwards 3/1 39 Claims 18 Drawmg F'gures PIVOTING DISC-TYPE HEART VALVE WITH TWO-PIECE BASE CROSS REFERENCE TO RELATED APPLICATION BACKGROUND OF INVENTION Heart valve prostheses are used in patients whose natural valves are damaged by congenital malformations or diseases and associated scarring and calcification. Numerous heart valve designs have been developed using either a ball, leaflet, or disc valving member. Each of these designs has certain advantages as well as deficiencies. They attempt but do not not achieve the duplication of the healthy natural heart valve. Problems of prosthetic valves are largely due to the shape and operating structure of the valves and the materials used in the valves. Some of the limitations of currently used heart valves are: 1) low efficiency and high pressure gradient across the valve; 2) high structural profile; 3) localized sites of wear and fatigue; 4) chemical breakdown and absorption of water and body fluids; 5) regions of blood stagnation; 6) structures that cause turbulence, regurgitation and eddy currents in the blood flow; 7) structure that can result in formation of clot streamers; and 8) malfunction of the movable valving member.

Durability is a crucial factor in the clinical applicability of any heart valve as a heart valve must open and close approximately four million times a year. It is imperative that the material used in the heart valve be immune from biochemical degradation and mechanical failure due to wear and fatigue of rubbing or flexing of the components of the valve. Biodegradation is interrelated with mechanical failure as biodegradation accelerates material fatigue and material breakdown. Rubbing and wear can accelerate the biochemical reaction, continually exposing new surfaces to corroding media.

Leaf-type valves, as disclosed by Lord in U.S. Pat. No. 2,682,057 and Servelle in British Patent No. 1,160,008, and disc-type valves, as disclosed by Wada in U.S. Pat. No. 3,445,863 and Bokros in U.S. Pat. No. 3,546,711, have low pressure gradients and fair flow characteristics. These valve designs are deficient as heart valves, as they have localized areas of wear and fatigue and have areas of blood stagnation.

DeLaszlo, in U.S. Pat. No. 3,526,906 discloses prosthetic implants made from carbonaceous materials. The heart valve implant has a rigid base of carbon or graphite carrying a silicone rubber ball or a disc having legs of plastic material. Bokros, in U.S. Pat. No. 3,546,71 1, shows a carbon coated valve having a gate pivoted on a fixed pin.

Kaster, in U.S. Pat. No. 3,476,143, discloses several pivoting disc heart valves. Each valve has a one-piece metal base and a plastic or metal pivoting disc. Bjork has described a similar disc-type valve in the Scandinavian Journal of Thoracic Cardiovascular Surgery, Volume 3 (1969), pages l-lO. The base and disc pivoting structures of these valves are not adapted to be made entirely of rigid carbon materials. Parts of either the base or the pivoting structure must be movable or flexible to permit assembly of the disc into the base. The plastic materials used in the discs are, over a period of time, susceptible to biodegradation as they tend to take up moisture and other body fluids, proteins and enzymes which will eventually deteriorate the disc, inhibiting the operation of the valve.

SUMMARY OF INVENTION The invention is directed to a heart valve prosthesis which has good efficiency with a low structure profile and a central flow pattern with a minimum of eddying, turbulence and regurgitation. The valve, when in the closed position, has limited retrograde or reverse flow to provide a constant washing action and motion of the blood. Materials used in the valve are lightweight in construction, have bio-compatibility, are nondegradable and have long term wearability.

One form of the heart valve incorporates a free floating silicon-alloyed Pyrolite carbon coated disc operatively associated with an annular valve housing. It has been found that Pyrolite carbons deposited as coatings or skins at lower temperatures on clean, smooth surfaces have excellent thromboresistance. These skins are impermeable to gases and liquids and are much stronger and wear resistant than graphite carbons. Pyrolite carbon has blood compatibility and is relatively inert toward blood plasmas, plasma proteins and plasma enzymes. Also, this material has dimensional stability, does not absorb moisture and body fluids and is compatible to both tissue and blood cells. Siliconalloyed Pyrolite carbon coatings are used to increase the wear resistance characteristics of the valve disc and valve base. The Pyrolite coatings or skins can be applied to a variety of substrates including metals, ceramics and graphite. These coatings are placed in a permanent compressive state to enhance the toughness and wearability of the coatings.

The heat valve has an annular base having an inner wall surrounding an opening through the base permitting the passage of blood in one direction through the valve. The free floating disc located in the opening is selectively movable to a first open position to allow flow of blood through said opening in one direction and movable to a second closed position to restrict the flow of blood in the opposite direction. When the disc is in the closed position, it is slightly smaller than the opening to allow for a limited or marginal retrograde or reverse flow of blood through the opening. This retrograde flow of blood is desirable to keep the blood in motion and prevent clog formation. The disc is a circular member having an annular uninterrupted peripheral edge and a substrate covered with a Pyrolite carbon coating. The disc is associated with pivot structures on the base to permit pivoting ,of the disc about a chordlike axis located between the diameter of the disc and an outer peripheral edge portion of the disc. The pivot structures also permit the disc to rotate freely about its center during its opening and closing movements. Cooperating with the pivot means are means to retain the disc in assembled relation with the base in the free floating manner.

In one form of the invention, the base has a first member having pivot structure for the disc. Positioned over and secured to the first member is a second member having the means for retaining the disc in free floating assembled relation with the base. The retaining means can include pivot structure for the disc. Both the first member and second member can be coated with a Pyrolite carbon skin.

IN THE DRAWINGS FIG. 1 is a top plan view of the heart valve of this invention showing the disc in the closed position;

FIG. 2 is a bottom plan view of the valve of FIG. 1;

FIG. 3 is a sectional view taken along the line 3-3 of FIG. 1;

FIG. 4 is a side view of the valve shown in FIG. 1 with the disc in the open position;

FIG. 5 is a sectional view similar to FIG. 3 showing the disc in the open position;

FIG. 6 is an enlarged fragmentary sectional view of the outer peripheral portion of the disc;

FIG. 7 is a top plan view of a modified heart valve of the invention;

FIG. 8 is a bottom plan view of the heart valve of FIG. 7;

FIG. 9 is a sectional view taken along the line 9-9 of FIG. 7;

FIG. 10 is a side elevational view of the heart valve shown in FIG. 7;

FIG. 11 is a sectional view of a heart valve similar to FIG. 9 showing the disc in the open position;

FIG. 12 is an enlarge sectional view of the valve housing in assembled relation with a sewing ring;

FIG. 13 is a top plan view of a further modified heart valve of the invention;

FIG. 14 is a sectional view taken along the line 14-14 of FIG. 13;

FIG. 15 is a sectional view similar to FIG. 14 showing the disc in the open position;

FIG. 16 is a top plan view of another heart valve of the invention;

FIG. 17 is a sectional view taken along the line 17-17 of FIG. 16; and

FIG. 18 is a sectional view taken along the line l8-l8 of FIG. 16.

Referring to the drawings, there is shown in FIGS. l-5 a one-way valve or heart valve adapted for use in either mitral or aortic positions of a human heart. The valve indicated generally at 20 has a base or annular housing 21 associated with a movable disc 22. The disc 22 is a valving member or occluder which moves angularly from a closed position as shown in FIG. 3 to an open position shown in FIG. 4 and then back to the closed position in response to differential fluid pressures on opposite sides of the valve. The disc 22 is mounted in a free floating relationship in the base, being free to rotateabout its center axis as it angularly moves between its open and closed positions to control one-way movement of blood through the valve.

Base 21 has an outer annular side wall 23 located between an upper outwardly directed annular flange 24 and a lower outwardly directed annular flange 26. A sewing collar or suture ring (not shown) is mounted on wall 23 to provide structure for receiving sutures used to implant the valve in the heart. Base 21 has an inside generally cylindrical wall 27 surrounding the passage or opening 28 through the base. Disc 22 is operatively located in the passage 28 to permit substantially free central flow of blood through the passage 28 when the disc is in the open position, as shown in FIG. 5, and substantially block reverse flow of blood through the opening 28 when the disc 22 is in the closed position, as shown in FIG. 3.

The disc 22 is a flat circular member having a circular outer peripheral edge 29. The peripheral edge 29 has an annular uninterrupted circumferential configuration and is joined to a substantially flat top surface 31 and a substantially flat bottom surface 32.

As shown in FIGS. 1, 2 and 3, the diameter of the disc 22 is slightly smaller than the opening 28 when the disc is in the closed position, leaving a small annular space 33 between the outer peripheral edge 29 of the disc and the adjacent portion of the inside wall 27 of the base. This small space allows for limited reverse or retrograde flow of blood through the valve opening 28 when the disc 22 is in its closed position. The retrograde flow of blood prevents stagnation in pockets or pools of blood adjacent the valve base, as the blood is continu ously moving through the valve passage 28.

The disc 22 is retained or held in free floating assembled relation with the base by pivot structures indicated generally at 34. The pivot structures 34 provide a pivot axis for the disc 22 that follows generally an imaginary chord line lying approximately an equal distance between the center of the valve passage 28 and the inside wall 27 measured along a transverse diametrical line. The pivot axis of the disc 22 can vary relative to the center of the disc during the opening and closing episodes of the disc as the disc has limited movement in its plane as it pivots. The pivot structures comprise upper or distal members 36 and 37 which extend over portions of the disc and into the opening. Members 36 and 37 are circumferentially spaced from each other.

Located generally adjacent the upper members 36 and 37- are lower or proximal pivot members 38 and 39. Members 38 and 39 project into the opening and extend adjacent portions of the lower side 32 of the disc. Pivot members 36 and 38 are projections or pivot legs which function as fulcrums for the disc during its opening and closing movements.

Pivot members 37 and 39 are substantially identical to pivot members 36 and 38. The following detailed description is limited to pivot members 36 and 38. As shown in FIGS. 2, 3 and 5, proximal pivot member 38 has a round fulcrum corner 41 joined to a top inclined face 42 and a generally upright face 43. Pivot member 36 has a fulcrum corner 44 facing the top face of the disc joining the inclined face 46 and a generally upright face 47. Faces 43 and 47 are generally parallel to each other. Faces 42 and 46 are generally parallel to each other. Substantially midway between the lower pivot members 38 and 39 is an inwardly directed stop or abutment 48 on housing 21 adapted to engage an outer peripheral portion of the disc 22. The lower pivot members 38 and 39 and stop 48 serve to support the disc in a generally inclined position with respect to the longitudinal axis of the passage 28 when the disc is in the closed position. Preferably this angle is about 18 from the horizontal plane of the base.

Disc 22 is maintained in free floating assembled relation with respect to the pivot structure 34 with retaining arms 49 and 51. Arms 49 and 51, integral with the top of the base 21, project upwardly and are inclined from the base in the direction of pivotal movement of the disc 22. Arms 49 and 51 each have inside surfaces or faces 52 and 53 which have a concave curvature larger than the curve or are of the peripheral portion of the disc 22. The surfaces 52 and 53 curve inwardly toward the center line of the disc as shown in FIG. 4 and are located outwardly of or above the diameter of the disc so that the disc is retained in assembled relation with the base at all positions between its open and closed positions. The surfaces 52 and 53 follow a helical or spiral path as the radius of the arc of the surfaces increases toward the outer ends of the arms. The curvature of the surfaces 52 and 53 approaches the curvature of the pivot arc of the disc when the disc is in the closed position. This structure permits the disc to float and move upwardly during its opening episode, as indicated by solid and broken lines in FIG. 4.

FIG. 6 is an enlarged cross section of a portion of the disc 22 showing the disc substrate 54 entirely covered with a Pyrolite carbon coating or skin 56. A Pyrolite carbon substrate bond 57 firmly and positively joins the coating 56 to the substrate 54. For example, the substrate 54 can be a polycrystalline graphite coated with silicon-alloyed Pyrolite carbon. The carbon coating can have a Pyrolite carbon prime layer covered with a Pyrolite carbon finish coat. The silicon-alloyed Pyolite carbon is deposited at low temperatures in two layers. The thermal coefficient of expansion of the substrate graphite is such that during the cooling after coating, the outer carbon layer is forced into a compressive state of stress which enhances the toughness and wear characteristics of the coating. The Pyrolite carbons are deposited in a fluidized bed from a hydrocarbon containing gaseous environment. These carbons are stronger and tougher than other bulk forms of carbon. The coatings can be applied to a variety of substrates including metal, ceramics and graphite. The substrates can have complex shapes without danger of delamination and cracking. The process of depositing carbons in this manner, developed by Gulf General Atomic Inc. of San Diego, California, is described in a publication entitled Control of Structure of Carbon For Use in Bioengineering published in Engineering in Medicine Bioceramics, New England College, Henniker, New Hampshire, August 1970.

In use, when the disc 22 is in the closed position, as shown in FIGS. 1, 2 and 3, it is held in an inclined position in the passage 28 by the top inclined faces 42 of the proximal pivot members 38 and 39 and stop 48. The annular uninterrupted peripheral edge 29 of the disc 22 is spaced a slight distance from the adjacent side wall 27 of the housing whereby a limited reverse or retrograde flow of blood flows through the passage 28. An increase in the pressure of blood on the proximal side of the disc 22 carries the disc 22 in an upward and angular direction along the excursional arc established by the inside surfaces 52 and 53 on the arms 49 and 51. The disc 22 pivots about distal pivot fulcrum corners 44. As the disc pivots to the open position, it is free to rotate about its central axis and move slightly in its plane. The entire disc moves a short distance upwardly as indicated by broken lines in FIG. 4. When the disc 22 is in the open position, it is at a slight incline with respect to the longitudinal axis of the base. Preferably the open angle of the disc 22 is between 75 and 80 with respect to the horizontal plane of the base. When the disc 22 is in the open position, it has a negligible obstruction to the flow of blood through the passage 28. The entire disc is laterally spaced or offset from the center of the axis. In the full open position, about one-fourth of the flow of blood passes through the smaller opening.

Referring to FIGS. 7-12, there is shown a modification of the pivoting disc heart valve indicated generally at 58. Valve 58 has an annular base or housing 59 and a pivoting disc 61 to control the flow of blood through the valve in one direction. The housing 59 is a twopiece structure having an inner member 62 carrying an outer member 63. Both the inner member 62 and the outer member 63 are formed from material that has a coating or skin of Pyrolite carbon. The inner member 62 and outer member 63 may be made by investment casting or machining procedures as separate members and then assembled to operatively locate the disc 61 within the housing. The inner member 62 has an inside circumferential wall 64 forming a passage or opening 66 through the housing. Projected outwardly from the wall 64 are first distal pivots 67 and 68 and second proximal pivots 69 and 71. Located midway between the pivots 69 and 71 is a stop 72 for holding disc 61 in an inclined position when it is closed, as shown in FIG. 9. The lower portion of inner member 62 has an outwardly directed annular flange 73 and a cylindrical outer wall or face 74.

As shown in FIG. 12, outer member 63 has inside circumferential wall or face 76 of a size to fit with a close fit over the outer annular wall 74. A bonding agent or adhesive 77, as carbon cement, is used to secure the inner member 62 to the outer member 63. A locator pin 78 positioned in aligned holes in the inner member 62 and the outer member 63 is used to circumferentially orient the outer member 63 with respect to the inner member 62. The upper portion of outer member 63 has an outwardly directed annular flange 79 which forms with the lower flange 73 a recess or groove 81 adapted to accommodate a suturing member or sewing ring indicated generally at 82. As shown in FIG. 12, su-

turing member 82 has a cover 83 held in groove 81 with a retaining sleeve 84. The cover 83 encloses a core of plastic material 86 that is compatible with human tissue and body fluids. The core 86 can be fluorosilicone rubber or similar synthetic resinous plastic material. The cover 83 is biologically inert porous material that is compatible with chemicals and fluids of the body and does not deteriorate with time. An example of the suturing member is disclosed in U.S. patent application Ser. No. 817,988, now US. Pat. No. 3,623,212.

The outer member 63 has upwardly directed side members or shields 87 and 88. The side member 87 extends from pivot members 67 and 69 toward thestop 72. In a similar manner, the side member 88 extends from pivot members 68 and 71 toward stop 72. Each side member hasa disc guide surface 89 which follows a large elliptical path to form the excursional arc of the disc. This path is larger than the arcuate dimensions of the outer peripheral edge 91 of the dis whereby the dischas limited floating movement during its opening episode. The guide surfaces 89 of side members 87 and 88 curve upwardly and inwardly so that they form retaining surfaces to hold the disc in floating assembled relation with the base. The surfaces 89 have a concave shape which is slightly larger than the curvature of the outer peripheral edge 91 of the disc.

As shownin FIG. 9, when the disc 61 is in the closed position, it rests on the top surfaces of the proximal pivots 69 and 71 and stop 72. The outer peripheral uninterrupted edge 91 of the disc is spaced a small distance 92 from the adjacent portions of the inside wall 64 of the housing, thereby providing a small annular space 92. When the disc 61 is closed, a limited amount of blood can flow through the opening 66.

The disc 61 has a substrate 93, preferably of graphite, covered with a coating or skin of Pyrolite carbon 94 similar to disc 22 shown in FIG. 6. The inner member 62 has a body or substrate 96, preferably of graphite, carrying a coating or skin 97 of Pyrolite carbon whereby all pivot portions and the stop 72 have a Pyrolite carbon skin. As shown in FIG. 12, the outer member 63 can have a substrate 98 covered with a coating or skin 99 of Pyrolite carbon.

In use, with the disc 61 in the closed position as shown in FIG. 9, an increase in the pressure of the blood on the proximal side of the disc 61 will angularly pivot the disc to the open position about an axis offset from the diameter of the disc. The blood is free to flow through passage 66 on both sides of the disc 61. The disc, as it pivots to the open position, is free to float upwardly and rotate around its central axis as the excursional arc provided by the guide surfaces 89 of the side members 87 and 88 is slightly larger than the arc of the peripheral edge 91 of the disc.

A decrease in the pressure of the blood on the proximal side of the disc 61 will quickly return the disc to its closed position. The disc will initially drop and pivot about proximal pivots 69 and 71 as a portion of the disc strikes the stop 72. During the closing episode of the disc, the disc is free to rotate about its central axis.

Referring to FIGS. 13, 14 and 15, there is shown a further modification of a heart valve indicated generally at 101 for controlling the flow of blood in one direction. The heart valve 101 has an annular housing or base 102 comprising an inner annular member 103 secured to an outer annular member 104. Members 103 and 104 have a continuous circumferential inner wall 106 forming a passage or opening 107 through the valve housing. Located within the passage 107 is a free floating disc 108 which moves from a closed position as shown in FIG. 14, to an open position, as shown in FIG. 15, to permit substantially free flow of blood in one direction through the opening 107.

The inner member 103 has a pair of proximal pivots or pivot members 109 and 1 l1. Pivot members 109 and 111 are projections that are directed a short distance into the opening 107. The lower edge of inner member 103 has an annularly directed flange 112. The upper edge of the inner member 103 has a cylindrical outer surface of face 113.

The outer member 104 has distal pivots or pivot member 114 and 116 which are located adjacent the pivot members 109 and 111 respectively. The distal pivots 114 and 116 project into the opening and are spaced from the proximal pivots by an amount to accommodate portions of the disc 108 to control the pivoting of the disc about an axis that is offset from the diameter of the disc. Pivots 109, 111, 114 and 116 follow the structure of pivots 36, 37, 38 and 39 shown in FIGS. 1, 2 and 3. This axis coincides generally with a chord-like line of the disc 108. Located midway along the large circumferential distance between pivots 114 and 116 is an inwardly directed stop or abutment 117. The stop 117, along with proximal pivots 109 and 1 11, hold the disc 108 in an inclined closed position. The outer member 104 has a cylindrical inner face that tits in a close fit over the cylindrical outer face 113. A bonding material, as an adhesive or cement, is used to secure the inner member to the outer member to form a one-piece annular housing or base for the valve. The outer member 104 has outwardly directed annular flange 119. Flanges 112 and 119 form sides of a recess or groove in the outer surface of the housing for the sewing ring or suturing member (not shown).

The disc 108 is retained in free floating relation with the base 102 by an inwardly directed arm 122 forming part of the outer member 104. The inner end of the arm 122 is curved downwardly and terminates in end portion or head 123. The end portion 123 is located in annular groove or recess 124 in the top face or side of disc 108. The groove is of a size that is slightly larger than the end portion 123 so that it permits a limited degree of lateral or sideways movement of the disc during its opening and closing. As shown in FIG. 13, groove 124 is generally concentric with the center of disc 108. The inner member 103, outer member 104 and arm 122 can be made of a substrate covered with a coating or skin of Pyrolite carbon.

The disc 108 has an annular uninterrupted outer peripheral edge 126 that is located a short distance from the inner wall 106 of the housing when the disc is in the closed position to provide a small annular space 127. This space permits a limited reverse or retrograde flow of blood through the valve when the disc is in the closed position. Disc 108 has a substrate, preferably of graphite, covered with a coating or skin of Pyrolite carbon.

The valve is assembled without bending, welding or adding parts. The two-piece housing 102 enables the disc 108 to be located between the pairs of pivot members 109, 114 and 111, 116 by mounting the housing members on each other with the disc positioned between the members.

Referring to FIGS. 16, 17 and 18, there is shown a further modification of the heart valve of the invention indicated generally at 200 for controlling the flow of blood. The heart valve 200 has an annular housing or base 201 comprising an inner member 202 carrying an outer member 203. The inner member 202 has an annular circumferential inner wall 204 forming a passage or opening 206 through the valve. Located within passage 206 is a disc 207 which pivots between open and closed positions to control the flow of blood in one direction through the opening 206.

The inner member 202 has circumferentially spaced proximal pivots 208 and 209 which project into opening 206 to form pivot members, projections, or pivot legs for controlling the pivotal movement of the disc 207 during the closing episode. The proximal pivots 208 and 209 provide fulcrums so that the pivotal movement of the disc 207 is about an axis that is offset from the diameter of the disc. The pivots 208 and 209 are identical in structure. The following description is limited to pivot 208. As shown in FIG. 18, pivot 208 has a rounded fulcrum corner 211 joined to an upwardly inclined top face 212 and a generally upright side sur-' face 213. An inwardly directed stop 214 projects from the inner wall 204 approximately midway between the pivots 208 and 209. When the disc is in the closed position, a portion of the disc rests on the stop 214 and top faces 212 of pivots 208 and 209.

Inner member 202 has a generally cylindrical outer face 216 and an outwardly directed lower flange 217. Outer member 203 of the housing has an upward annular flange 218 and inner cylindrical surface 219 of a size to closely tit over the cylindrical outer base 216 whereby the outer member is carried or mounted on the inner member 202. A sealing material, cement, adhesive or like material, is used to secure or bond the inner member 202 to the outer member 203 to form a unitary housing. The flanges 217 and 218 are located on opposite sides of an annular outer groove or recess 221 for accommodating the suturing member or sewing ring (not shown).

As shown in FIGS. 16 and 17, the upper portion of the outer member 203 has a pair of inwardly directed legs 222 and 223 which extend over portions of the disc 207. Legs 222 and 223 extend generally toward each other and fit into generally upright slots 225 in the inner member 202. Slots 225 circumferentially locate the inner member 202 with the outer member 203. The outer ends of legs 222 and 223 have downwardly directed portions or extensions 224 and 226 located in a generally circular recess 227 in the top of disc 207. Disc 207 has a generally annular upright wall 228 forming the side of the recess. The end portions 224 and 226 extend down into the recess and engage separate portions of the wall 228 to hold the disc in a substantially free floating pivotal relationship in the housing and provide pivot portions for the disc as it moves from the closed position to the open position. The end portions are located in a generally loose fit with respect to the wall 228 whereby the disc is free to pivot and rotate about its axis as it moves between the open and closed positions, as shown in broken and full lines in FIG. 18.

Disc 207 has an outer peripheral edge 229 having a smooth, uninterrupted circular configuration. When disc 207 is in the closed position, the outer peripheral edge 229 is spaced a small distance 231 from the adjacent portions of the inside wall 204. This distance or space is sufficient to permit limited reverse or retrograde fiow of blood through the valve when disc 207 is in the closed position. As shown in FIG. 18, when the disc 207 is in the closed position, it is inclined approximately 18 with respect to the horizontal plane of the base 201. When the disc 207 is in the open position, it pivots about an axis offset from the center of the disc to an angle of approximately 80 with respect to the horizontal plane of the base 201. With the disc 207 in the open position, the valve has substantially free central flow of bloodthrough the large portion of the opening 204. The smaller portion of the opening is substantially unobstructed, whereby the laminar flow characteristics of the blood are maintained.

Disc 207 is a carbon disc having a substrate 232, preferably of graphite, completely surrounded by a coating or skin 233 of Pyrolite carbon. The substrate and coating can be the same as described for the disc 22 shown in FIG. 6. The inner member and outer member of the housing are also formed of carbon material with each member having a substrate and a coating or skin of Pyrolite carbon. All the parts of the valve can be made of carbon. It is not necessary that any portion of the valve be hinged or bent to assemble the disc in a free floating pivotal relationhip with respect to the base. The disc 207 is located on proximal pivots 208 and 209 before the housing 204 is assembled. The outer housing member 203 is assembled on inner member 204 to locate the disc in the pivotal position and retain the disc in assembled relation with respect to the valve housing.

In use, with the disc 207 in the closed position, as shown in full lines in FIG. 18, an increase in the pressure of the blood on the proximal side of the disc will initially raise the disc. Portions of the disc come in contact with end portions 224 and 226 of legs 222 and 223. The disc will then be angularly moved to an open position, as shown in broken lines, about an axis offset from the center of the disc and spaced from the outer edge of the disc. The blood is free to flow through the passage 204 on opposite sides of the disc. As the disc opens, it is free to rotate about its central axis, thereby eliminating any localized wear and minimizing turbulence in the flow of the blood through passage 204. A decrease in the pressure of the blood on the proximal side of the disc 207 causes the disc to initially fall and then quickly return to its closed position, pivoting about the fulcrum comers 211 of the proximal pivots 208 and 209. As the disc pivots to the closed position, it can move slightly in a forward direction as the end portions 224 and 226 have a loose fit with respect to the wall 228 in the top of the disc. The disc will continue pivoting in the downward direction until the disc engages the top faces 212 and stop 214.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

l. A heart valve for controlling the flow of blood comprising: base means having an internal wall forming a passage through the base means, disc means located in said passage selectively movable to an open position to allow flow of blood through said passage in one direction and to a closed position to restrict the flow of blood through said passage in the opposite direction, said disc means having an annular uninterrupted outer peripheral edge cooperating with said internal wall to close said passage when the disc means is in the closed position, pivot means attached to the base means allowing pivotal movement of the disc means between its open position and closed position and rotational movement relative to the axis thereof, and retaining means for holding the disc means in assembled relation with the base, said retaining means including means for guiding the disc means along a curved path between the open position and closed position thereof and allowing the disc means greater lateral movement when the disc means is in the open position than when the disc means is in the closed position, said base means having a first annular member, at least part of said pivot means being attached to the first annular member, and a second annular member mounted on the first annular member, means securing the first annular member to the second annular member, said retaining means for holding the disc means in assembled relation with the base being attached to the second annular member.

2.;The heart valve of claim 1 wherein: said retaining means for holding the disc means in assembled relation with the base'comprise side shields secured to the sec ond member, said shields having the means for guiding the disc means, said means for guiding the disc means including concave curved surfaces cooperating with the disc means to guide the movement of the disc means between its open and closed positions.

3. The heart valve of claim 1 wherein: said retaining means for holding the disc means in assembled relation with the base comprise arm means secured to the second member, said disc means having a recess for accommodating a portion of the arm means.

4. The heart valve of claim 3 wherein: the arm means have portions on which the disc means pivots from the closed position to the open position.

5. The heart valve of claim 1 wherein: the outer peripheral portion of the disc means is spaced inwardly from the inner wall of the base means when the disc means is in the closed position, thereby allowing limited reverse flow of blood through the opening in the base means when the disc means is in the closed position.

6. The heart valve of claim 1 including: means on the base means engageable by the disc means when the disc means is in the closed position to hold the disc means in an inclined position with respect to the plane normal to the axis of the passage in the base means.

7. The heart valve of claim 1 wherein: the pivot means have upwardly directed faces which engage portions of the disc means in the extreme open position to thereby define the maximum open position of the disc.

8. The heat valve of claim 1 wherein: the pivot means include pivot members on the base means which engage the disc means when the disc means is in the closed position to hold the disc means in an inclined position with respect to a plane normal of the axis of the opening of the base means.

9. The heart valve of claim 1 wherein: said disc means has a substrate and a Pyrolite carbon coating covering the substrate.

10. The heart valve of claim 1 wherein: the means for guiding the disc means has at least one surface with a concave curvature larger than the arc of the outer peripheral edge of the disc means.

11. The heart valve of claim 1 wherein: said pivot means comprise pairs of pivot members on the first member of the base means for pivoting the disc about an axis located between the diameter of the disc means and an outer peripheral edge portion of the disc means.

12. The heart valve of claim 1 wherein: said pivot means comprise distal pivot means on the first member of the base means and proximal pivot means on the second member of the base means.

13. The heart valve of claim 12 wherein: said distal pivot means are part of the retaining means.

14. The heart valve of claim 12 wherein: said pivot means are located on the base means and positioned for pivoting the disc about an axis located between the diameter of the disc means and an outer peripheral portion of the disc means.

15. The heart valve of claim 1 wherein: said disc means and base means have Pyrolite carbon coatings.

16. A heart valve for controlling the flow of blood comprising: base means having an internal wall forming a passage through the base means, disc means selectively movable to an open position to allow flow of blood through said passage in one direction and to a closed position to restrict the flow of bloodthrough said passage in the opposite direction, said disc means having an annular uninterrupted outer peripheral edge cooperating with said internal wall to close said passage when the disc means is in the closed position and allowing rotation of the disc means about its central axis, means attached to the base means for holding the disc means in assembled relation with the base and allowing pivotal movement of the disc means between its open position and closed position and rotational movement of the disc means relative to the axis thereof, said means for holding the disc means including means for guiding the disc means along a curved path between the open position and closed position thereof and allowing the disc means greater lateral movement when the disc means is in the open position than when the disc means is in the closed position, said base means having a first annular member connected to at least part of .said means for holding and allowing pivotal movement of the disc means, and a second annular member connected to another part of the means for holding and allowing pivotal movement of the disc means, said second annular member being mounted in telescopic relation with the first annular member, and means for securing the first annular member to the second annular member.

17. The heart valve of claim 16 wherein: said means for holding the disc means in assembled relation with the base comprise side shields secured to the first member, said shields having the means for guiding the disc means, said means for guiding the disc means including concave curved surfaces cooperating with the disc means to guide the movement of the disc means between its open and closed positions.

18. The heart valve of claim 17 wherein: said surfaces have a concave curvature larger than the arc of the outer peripheral edge of the disc means.

19. The heart valve of claim 16 wherein: said means for holding the disc means in assembled relation with the base comprise arm means secured to the first member, said disc means having a recess for accommodating a portion of the arm means.

20. The heart valve of claim 19 wherein: the arm means have portions on which the disc means pivots from the closed position to the open position.

21. The heart valve of claim 16 wherein: the outer peripheral portion of the disc means is spaced inwardly from the inner wall of the base means when the disc means is in the closed position, thereby allowing limited reverse flow of blood through the opening in the base means when the disc means is in the closed position.

22. The heart valve of claim 16 including: means on the base means engageable by the disc means when the disc means is in the closed position to hold the disc means in an inclined position with respect to the plane normal to the axis of the passage in the base means.

23. The heart valve of claim 16 wherein: the means for holding and allowing pivotal movement of the disc means have upwardly directed faces which engage portions of the disc means in the extreme open position to thereby define the maximum open position of the disc.

24. The heart valve of claim 16 wherein: the means for holding and allowing pivotal movement of the disc means include pivot members on the base means which engage the disc means when the disc means is in the closed position to hold the disc means in an inclined position with respect to a plane normal of the axis of the opening of the base means.

25. The heart valve of claim 16 wherein: said means for holding and allowing pivotal movement of the disc means comprise pairs of pivot members on the first member of the base means for pivoting the disc means about an axis located between the diameter of the disc means and an outer peripheral edge of the disc means.

26. The heart valve of claim 16 wherein: said means for holding and allowing pivotal movement of the disc means comprise pairs of pivot members on the first member of the base means for pivoting the disc means about an axis located between the diameter of the disc means and an outer peripheral edge of the disc means.

29. A heart valve for controlling the flow of blood comprising: base means having an inner wall surrounding an opening through the base means allowing blood to flow through the base means, said base means having a first annular member, a second annular member mounted on the first annular member, means securing the first annular member to the second annular mem- 7 her, disc means positioned in said opening operable to selectively move to a first open position to allow the flow of blood through said opening in one direction and to a second closed position to restrict the flow of blood in the opposite direction through said opening, means for maintaining the disc means in assembled relation with the base means in a manner so that the disc means is free to rotate relative to its central axis and is free to pivot between the open position and closed position thereof, said means for maintaining the disc means in assembled relation with the base means cooperating with the disc means to hold the disc means in an inclined position with respect to the plane normal to the axis of the opening in the base means when the disc means is in the closed position, said means for maintaining the disc means in assembled relation with the base means comprising first means secured to the first member of the base means and located on one side of the disc means engageable with said disc means during movement of the disc means from the closed position to the open position for controlling the pivotal movement of the disc means, second means secured to the second member of the base means and located on the opposite side of said disc means contacting said disc means during movement of the disc means from the open position to the closed position, said second means having fulcrum surfaces cooperating with said disc means during the closing movement to provide pivotal movement of the disc means about a location offset from the diameter of the disc means and spaced inwardly from a portion of the peripheral edge of the disc means and allowing rotation of the disc means relative to its central axis, and third means having surfaces for guiding the disc means along a curved path betweenthe open position and closed position thereof and allowing the disc means greater lateral movement when the disc means is in the open position than when the disc means is in the closed position.

30. The heart valve of claim 29 wherein: the third means are means located on opposite sides of the base means, said last means projected upwardly and curved inwardly and having an inside surface following a spiral path larger than the curvature of the outer peripheral edge of the disc means.

31. The heart valve of claim 30 wherein: the spiral path on the inside surface approaches the curvature of the outer peripheral edge of the disc means when the disc means is in the closed position.

32. The heart valve of claim 29 wherein: the second means includes a pair of legs projected into said opening, each leg having a fulcrum surface.

33. The heart valve of claim 29 wherein: said disc means has an outer skin of Pyrolite carbon.

34. The heart valve of claim 29 wherein: said disc means has an annular uninterrupted outer peripheral edge spaced inwardly from the inner wall of the base means when the disc is in the closed position, thereby providing an annular space between the outer peripheral edge and the inner wall allowing limited annular reverse flow of blood through the annular space when the disc means is in the closed position.

35. The heart valve of claim 29 wherein: the disc means has an annular curved wall spaced inwardly from the outer peripheral edge of the disc means, said first means of the means for maintaining the disc means in assembled relation with the base being engageable with said wall during movement of the disc means from the closed position to the open position.

36. The heart valve of claim 29 wherein: the first means of the means for maintaining the disc means in assembled relation with the base means comprises a pair of inwardly directed members, said members having portions engageable with said disc means during movement of the disc means from the closed position to the open position.

37. The heart valve of claim 29 wherein: said base means has an outer skin of Pyrolite carbon and said disc means has an outer skin of Pyrolite carbon.

38. The heart valve of claim 29 wherein: one of said first or second members has at least one inwardly directed stop means engageable with the disc means when the disc means is in the closed position.

39. The heart valve of claim 29 wherein: said means for holding and allowing pivotal movement of the disc means provides for pivoting of the disc means about an axis located between the diameter of the disc means and an outer peripheral edge of the disc means.

Po-ww -UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,835,475 Dated September 17, 1974 Invent-ms) Francis w. Child It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 38, "heat" should be -he art--.

Column 5, line 21, "pjolitc" should be -Pyr0-ll,te-.

Claim 8, line 1, "heat" should be --hcart--.

Signed and sealed this 12th day of November 1974.

(SEAL) Attest:

MCCOY g4. GIBSON JR. 0. MARSHALL DANN Attestlng Officer Commissioner of Patents 

1. A heart valve for controlling the flow of blood comprising: base means having an internal wall forming a passage through the base means, disc means located in said passage selectively movable to an open position to allow flow of blood through said passage in one direction and to a closed position to restrict the flow of blood through said passage in the opposite direction, said disc means having an annular uninterrupted outer peripheral edge cooperating with said internal wall to close said passage when the disc means is in the closed position, pivot means attached to the base means allowing pivotal movement of the disc means between its open position and closed position and rotational movement relative to the axis thereof, and retaining means for holding the disc means in assembled relation with the base, said retaining means including means for guiding the disc means along a curved path between the open position and closed position thereof and allowing the disc means greater lateral movement when the disc means is in the open position than when the disc means is in the closed position, said base means having a first annular member, at least part of said pivot means being attached to the first annular member, and a second annular member mounted on the first annular member, means securing the first annular member to the second annular member, said retaining means for holding the disc means in assembled relation with the base being attached to the second annular member.
 2. The heart valve of claim 1 wherein: said retaining means for holding the disc means in assembled relation with the base comprise side shields secured to the second member, said shields having the means for guiding the disc means, said means for guiding the disc means including concave curved surfaces cooperating with the disc means to guide the movement of the disc means between its open and closed positions.
 3. The heart valve of claim 1 wherein: said retaining means for holding the disc means in assembled relation with the base comprise arm means secured to the second member, said disc means having a recess for accommodating a portion of the arm means.
 4. The heart valve of claim 3 wherein: the arm means have portions on which the disc means pivots from the closed position to the open position.
 5. The heart valve of claim 1 wherein: thE outer peripheral portion of the disc means is spaced inwardly from the inner wall of the base means when the disc means is in the closed position, thereby allowing limited reverse flow of blood through the opening in the base means when the disc means is in the closed position.
 6. The heart valve of claim 1 including: means on the base means engageable by the disc means when the disc means is in the closed position to hold the disc means in an inclined position with respect to the plane normal to the axis of the passage in the base means.
 7. The heart valve of claim 1 wherein: the pivot means have upwardly directed faces which engage portions of the disc means in the extreme open position to thereby define the maximum open position of the disc.
 8. The heat valve of claim 1 wherein: the pivot means include pivot members on the base means which engage the disc means when the disc means is in the closed position to hold the disc means in an inclined position with respect to a plane normal of the axis of the opening of the base means.
 9. The heart valve of claim 1 wherein: said disc means has a substrate and a Pyrolite carbon coating covering the substrate.
 10. The heart valve of claim 1 wherein: the means for guiding the disc means has at least one surface with a concave curvature larger than the arc of the outer peripheral edge of the disc means.
 11. The heart valve of claim 1 wherein: said pivot means comprise pairs of pivot members on the first member of the base means for pivoting the disc about an axis located between the diameter of the disc means and an outer peripheral edge portion of the disc means.
 12. The heart valve of claim 1 wherein: said pivot means comprise distal pivot means on the first member of the base means and proximal pivot means on the second member of the base means.
 13. The heart valve of claim 12 wherein: said distal pivot means are part of the retaining means.
 14. The heart valve of claim 12 wherein: said pivot means are located on the base means and positioned for pivoting the disc about an axis located between the diameter of the disc means and an outer peripheral portion of the disc means.
 15. The heart valve of claim 1 wherein: said disc means and base means have Pyrolite carbon coatings.
 16. A heart valve for controlling the flow of blood comprising: base means having an internal wall forming a passage through the base means, disc means selectively movable to an open position to allow flow of blood through said passage in one direction and to a closed position to restrict the flow of blood through said passage in the opposite direction, said disc means having an annular uninterrupted outer peripheral edge cooperating with said internal wall to close said passage when the disc means is in the closed position and allowing rotation of the disc means about its central axis, means attached to the base means for holding the disc means in assembled relation with the base and allowing pivotal movement of the disc means between its open position and closed position and rotational movement of the disc means relative to the axis thereof, said means for holding the disc means including means for guiding the disc means along a curved path between the open position and closed position thereof and allowing the disc means greater lateral movement when the disc means is in the open position than when the disc means is in the closed position, said base means having a first annular member connected to at least part of said means for holding and allowing pivotal movement of the disc means, and a second annular member connected to another part of the means for holding and allowing pivotal movement of the disc means, said second annular member being mounted in telescopic relation with the first annular member, and means for securing the first annular member to the second annular member.
 17. The heart valve of claim 16 wherein: said means for holding the disc means in assembled relation with the base comprise side shields secured to the fiRst member, said shields having the means for guiding the disc means, said means for guiding the disc means including concave curved surfaces cooperating with the disc means to guide the movement of the disc means between its open and closed positions.
 18. The heart valve of claim 17 wherein: said surfaces have a concave curvature larger than the arc of the outer peripheral edge of the disc means.
 19. The heart valve of claim 16 wherein: said means for holding the disc means in assembled relation with the base comprise arm means secured to the first member, said disc means having a recess for accommodating a portion of the arm means.
 20. The heart valve of claim 19 wherein: the arm means have portions on which the disc means pivots from the closed position to the open position.
 21. The heart valve of claim 16 wherein: the outer peripheral portion of the disc means is spaced inwardly from the inner wall of the base means when the disc means is in the closed position, thereby allowing limited reverse flow of blood through the opening in the base means when the disc means is in the closed position.
 22. The heart valve of claim 16 including: means on the base means engageable by the disc means when the disc means is in the closed position to hold the disc means in an inclined position with respect to the plane normal to the axis of the passage in the base means.
 23. The heart valve of claim 16 wherein: the means for holding and allowing pivotal movement of the disc means have upwardly directed faces which engage portions of the disc means in the extreme open position to thereby define the maximum open position of the disc.
 24. The heart valve of claim 16 wherein: the means for holding and allowing pivotal movement of the disc means include pivot members on the base means which engage the disc means when the disc means is in the closed position to hold the disc means in an inclined position with respect to a plane normal of the axis of the opening of the base means.
 25. The heart valve of claim 16 wherein: said means for holding and allowing pivotal movement of the disc means comprise pairs of pivot members on the first member of the base means for pivoting the disc means about an axis located between the diameter of the disc means and an outer peripheral edge of the disc means.
 26. The heart valve of claim 16 wherein: said means for holding and allowing pivotal movement of the disc means comprise pairs of pivot members on the first member of the base means for pivoting the disc means about an axis located between the diameter of the disc means and an outer peripheral edge of the disc means.
 27. The heart valve of claim 26 wherein: said pivot means are located on the base means and positioned for pivoting the disc about an axis located between the diameter of the disc means and an outer peripheral portion of the disc means.
 28. The heart valve of claim 16 wherein: said disc means and base means have Pyrolite carbon coatings.
 29. A heart valve for controlling the flow of blood comprising: base means having an inner wall surrounding an opening through the base means allowing blood to flow through the base means, said base means having a first annular member, a second annular member mounted on the first annular member, means securing the first annular member to the second annular member, disc means positioned in said opening operable to selectively move to a first open position to allow the flow of blood through said opening in one direction and to a second closed position to restrict the flow of blood in the opposite direction through said opening, means for maintaining the disc means in assembled relation with the base means in a manner so that the disc means is free to rotate relative to its central axis and is free to pivot between the open position and closed position thereof, said means for maintaining the disc means in assembled relation with the base means cooperating with the disc means to hold the disc means in an inclined position witH respect to the plane normal to the axis of the opening in the base means when the disc means is in the closed position, said means for maintaining the disc means in assembled relation with the base means comprising first means secured to the first member of the base means and located on one side of the disc means engageable with said disc means during movement of the disc means from the closed position to the open position for controlling the pivotal movement of the disc means, second means secured to the second member of the base means and located on the opposite side of said disc means contacting said disc means during movement of the disc means from the open position to the closed position, said second means having fulcrum surfaces cooperating with said disc means during the closing movement to provide pivotal movement of the disc means about a location offset from the diameter of the disc means and spaced inwardly from a portion of the peripheral edge of the disc means and allowing rotation of the disc means relative to its central axis, and third means having surfaces for guiding the disc means along a curved path between the open position and closed position thereof and allowing the disc means greater lateral movement when the disc means is in the open position than when the disc means is in the closed position.
 30. The heart valve of claim 29 wherein: the third means are means located on opposite sides of the base means, said last means projected upwardly and curved inwardly and having an inside surface following a spiral path larger than the curvature of the outer peripheral edge of the disc means.
 31. The heart valve of claim 30 wherein: the spiral path on the inside surface approaches the curvature of the outer peripheral edge of the disc means when the disc means is in the closed position.
 32. The heart valve of claim 29 wherein: the second means includes a pair of legs projected into said opening, each leg having a fulcrum surface.
 33. The heart valve of claim 29 wherein: said disc means has an outer skin of Pyrolite carbon.
 34. The heart valve of claim 29 wherein: said disc means has an annular uninterrupted outer peripheral edge spaced inwardly from the inner wall of the base means when the disc is in the closed position, thereby providing an annular space between the outer peripheral edge and the inner wall allowing limited annular reverse flow of blood through the annular space when the disc means is in the closed position.
 35. The heart valve of claim 29 wherein: the disc means has an annular curved wall spaced inwardly from the outer peripheral edge of the disc means, said first means of the means for maintaining the disc means in assembled relation with the base being engageable with said wall during movement of the disc means from the closed position to the open position.
 36. The heart valve of claim 29 wherein: the first means of the means for maintaining the disc means in assembled relation with the base means comprises a pair of inwardly directed members, said members having portions engageable with said disc means during movement of the disc means from the closed position to the open position.
 37. The heart valve of claim 29 wherein: said base means has an outer skin of Pyrolite carbon and said disc means has an outer skin of Pyrolite carbon.
 38. The heart valve of claim 29 wherein: one of said first or second members has at least one inwardly directed stop means engageable with the disc means when the disc means is in the closed position.
 39. The heart valve of claim 29 wherein: said means for holding and allowing pivotal movement of the disc means provides for pivoting of the disc means about an axis located between the diameter of the disc means and an outer peripheral edge of the disc means. 